Robotic surgical systems have been used in minimally invasive medical procedures. Some robotic surgical systems include a console supporting a robot arm, and at least one end effector such as forceps or a grasping tool that is mounted to the robot arm via a wrist assembly. During a medical procedure, the end effector and the wrist assembly are inserted into a small incision (via a cannula) or a natural orifice of a patient to position the end effector at a work site within the body of the patient.
Cables extend from the robot console, through the robot arm, and connect to the wrist assembly and/or end effector. In some instances, the cables are actuated by means of motors that are controlled by a processing system including a user interface for a surgeon or clinician to be able to control the robotic surgical system including the robot arm, the wrist assembly and/or the end effector.
In some instances, the wrist assembly provides three degrees of freedom for movement of the end effector through the use of cables or cable pairs, one for each degree of freedom. For example, for grasping or cutting end effectors, the wrist assembly provides the three degrees of freedom by allowing changes to a pitch, a yaw, and an opening and closing of the end effector.
Prior to or during use of the robotic system, surgical instruments are selected and connected to instrument drive units of each robot arm. For proper installation to be completed, certain connecting features of the surgical instrument must be matingly engaged to corresponding connecting features of the instrument drive unit. Once these features are matingly engaged, the instrument drive unit can drive the actuation of the surgical instrument. However, cables for actuating functions of the surgical instrument can lose their tension force and become slack upon manipulation of the jaw members of the surgical instrument, for example.
Accordingly, there is a need for instrument drive units that maintain tension in these cables both in a passive state and in an active state.